As an amount of data accompanied by an information processing is increased in recent years, the size of a storage device where the data are written is being increased as well. Further, the storage device includes two or more redundant connection routes in preparation for an occurrence of a fault and switches the connection route when the fault is detected. For example, the storage device is equipped with a redundancy for the fault occurrence by being provided with a forward connection route in which equipment are connected in cascade in a forward direction and a backward connection route in which equipment are connected in cascade in a backward direction which is opposite to the forward direction.
As described above, in a storage device, the number of constitutional equipment such as a controller module or a disk enclosure is increasing and a connection route which connects the constitutional equipment is becoming complicated. In the storage device, a controller module is utilized as, for example, a connection monitoring device which monitors a connection of a monitored device such as, for example, a disk enclosure and detects an erroneous connection of the monitored device in coping with the increase in the number of constitutional equipment or complication of the connection route.
Related technologies are disclosed in, for example, Japanese Laid-Open Patent Publication No. 2006-146489, Japanese Laid-Open Patent Publication No. 2005-222379, and Japanese Laid-Open Patent Publication No. 2007-272702.